Charged particle beam devices are used for analyzing and examining objects (hereinafter also called samples) in order to obtain insights with regard to the properties and behavior of the objects under specific conditions. One of those charged particle beam devices is an electron beam device, in particular a scanning electron microscope (also known as SEM).
In an SEM, an electron beam (hereinafter also called primary electron beam) is generated using a beam generator. The electrons of the primary electron beam are accelerated to a predeterminable energy and focused by a beam guiding system, in particular an objective lens, onto a sample to be analyzed (that is to say an object to be analyzed). A high-voltage source having a predeterminable acceleration voltage is used for acceleration purposes. Using a deflection unit, the primary electron beam is guided in a raster-type fashion over a surface of the sample to be analyzed. In this case, the electrons of the primary electron beam interact with the material of the sample to be analyzed. In particular, interaction particles and/or interaction radiation arise(s) as a consequence of the interaction. By way of example, electrons are emitted by the sample to be analyzed (so-called secondary electrons) and electrons of the primary electron beam are backscattered at the sample to be analyzed (so-called backscattered electrons). The secondary electrons and backscattered electrons are detected and used for image generation. An image of the sample to be analyzed is thus obtained.
The interaction radiation comprises X-rays and/or cathodoluminescence light and may be detected with a radiation detector. When measuring X-rays with the radiation detector, in particular energy-dispersive X-ray spectroscopy (also known as EDS or EDX) may be carried out. EDX is an analytical analysis method used for the elemental analysis or chemical characterization. Furthermore, when measuring X-rays with the radiation detector, in particular wavelength-dispersive X-ray spectroscopy (also known as WDS or WDX) may be carried out. WDX is also an analytical analysis method used for the elemental analysis or chemical characterization. EDX and WDX are often used as analytical analysis methods for analyzing rocks in the field of mineralogy. It is possible to identify the composition of a mineral grain, which is important information, in particular for a petrologist who needs to accurately determine the mineralogy of a rock.
An ion beam device is also known from the prior art. The ion beam device comprises an ion beam column having an ion beam generator. Ions are generated which are used for processing a sample (for example for removing a layer of the sample or for depositing material on the sample, wherein the material is provided by a gas injection system) or else for imaging.
Furthermore, it is known from the prior art to use combination devices for processing and/or for analyzing a sample, wherein both electrons and ions can be guided onto a sample to be processed and/or to be analyzed. By way of example, it is known for an SEM to be additionally equipped with an ion beam column as mentioned above. The SEM serves, in particular, for observing the processing, but also for further analysis of the processed or non-processed sample. Electrons may also be used for depositing material. This is known as electron beam induced deposition (EBID). Ions may also be used for depositing material.
When analyzing an object with a charged particle beam device, further methods may be used for identifying characteristics of an object. Electron backscatter diffraction (also known as EBSD) is a technique used to analyze the crystallographic orientation and the crystal structure of materials. It is known to use EBSD in an SEM having an EBSD detector. The EBSD detector may comprise a CCD chip. The EBSD detector detects electrons backscattered from the object and generates detection signals. Based on the detection signals, an electron backscatter diffraction pattern (also known as EBSP) is generated. The EBSP comprises information about Kikuchi bands corresponding to lattice diffraction planes of an object to be analyzed.
A further technique for analyzing an object is known as transmission Kikuchi diffraction (also known as TKD). When using TKD, an electron beam is guided to an object which is thin enough to be transparent to a sufficient part of the electrons of the electron beam. In other words, electrons of the electron beam may transmit through the object. For example, the object is a foil. The object is positioned approximately horizontal with respect to the sample chamber. Alternatively, the object is slightly tilted away from the EBSD detector by an angle of up to 20° or up to 30°. The scattered and transmitted electrons of the electron beam emerging from a bottom side of the object are detected using the EBSD detector. The EBSD detector is positioned off-axis with respect to the optical axis of the electron beam guided to the object. In particular, the EBSD detector is positioned below the object and below a position which is normally used for EBSD when generating an EBSP as mentioned above. Using TKD, the EBSD detector generates detector signals used for acquiring and recording diffraction patterns of the object, the diffraction patterns being projected from the bottom side of the object to the EBSD detector.
EDX, WDX and EBSD are limited with respect to their analytical resolution by the sampling volume, wherein the resolution is about 1 μm, as explained further below. The landing energy of electrons of an SEM used for EDX, WDX and EBSD is often chosen in such a way that the electrons penetrate rather deep into the object and generate X-rays from a volume unit of the object comprising an extension of about 1 μm in a first direction, in a second direction and in a third direction. Therefore, the volume unit comprises dimensions of approximately 1 μm×1 μm×1 μm. However, this resolution may not be sufficient for analysis of materials, in particular in oil and gas applications since, for example, sedimentary rocks may comprise features of interest having a dimension much smaller than 1 μm.
A charged particle beam device such as a combination of an SEM with an ion beam column may be used to generate high resolution 3D data sets by sequentially removing material from the object, exposing a surface of the object and generating an image of the surface. The resolution of the image may be 1 nm to 3 nm. Unfortunately, as mentioned above, the analytical methods such as EDX, WDX and EBSD do not offer a resolution in nm-range, thus making it difficult to generate high resolution 3D analytical data sets obtained by EDX, WDX and EBSD.
It is desirable to provide a method for analyzing an object using a charged particle beam device and a charged particle beam device for carrying out the method which make it possible to obtain a high resolution 3D analytical data set based on analysis methods such as, for example, EDX, WDX and EBSD.